Do Your Code Like A User Is Stupid

Developers spend hours designing "intuitive" interfaces, convinced that no user could possibly misunderstand them. Then reality strikes with the subtlety of a truck carrying lumber sideways. Users will find ways to break your system that you couldn't imagine in your worst fever dream. This is why we have error messages like "Please don't hold your phone upside down while shaking it violently and trying to log in." Murphy's Law of UI: if there's a wrong way to use it, someone will find it... and then file a support ticket.